The objective of the In Vitro Assay Core is to assess the ability of antibodies to affect gamete function. The Core will evaluate antibodies generated at three different step in the immunocontraceptive development pathway. 1. Discovery phase: monoclona antibodies and antisera against novel gamete antigens. 2. Immunogenicity testing: antibodies raised against recombinant proteins or synthetic peptides. 3. Fertility trials: antisera from fertility trials in mice, non-human primates, and human clinical trials. The path from initial identification of a gamete antigen to use of the immunogen in a contraceptive vaccine formulation is both time consuming and expensive. The services offered by the In Vitro Assay Core will provide investigators with an important screening tool to evaluate each antigen's contraceptive vaccine potential at an early stage in the developmental pathway and to triage immunogens that do not affect gamete function. Additionally, the Core will monitor the effects of antibodies raised during fertility trials on gamete function. The assays which the Core will perform to achieve these objectives are: indirect immunofluorescence, flow cytometry, sperm agglutination, Tru-Trax cervical mucus penetration, sperm immobilization/motility, mouse in vitro fertilization (IVF), zona-free hamster egg penetration, and human sperm hemi-zona binding.